Add a vscode extensions.json with the recommended extensions.

[ArnoPeters]

There are 2 Visual Studio Code extensions for this repo recommended in the documentation.
One of them seems to have had a name change, and it takes a few extra steps and clicking around to manually search and install them from the VSCode marketplace.

I would suggest adding a /.vscode/extensions.json with those recommendations - based on the extension ID - this will trigger Visual Studio Code to display a notification asking developers to choose if they want to install the exact extensions that were recommended on repo open.

More info about the extensions.json file can be found here: https://code.visualstudio.com/docs/editor/extension-marketplace#_workspace-recommended-extensions